IDAA1c of 9 or below misses many youth in partial remission

Design

Cross-sectional diagnostic accuracy analysis within a cohort study

Population

422 youth with diabetes in SEARCH, C-peptide measured within 12 months of diagnosis

Primary outcome

Sensitivity and specificity of IDAA1c 9 or below for C-peptide-defined partial remission

Effect

Overall sensitivity 61%, specificity 79%, AUC 0.77; with overweight or obesity sensitivity 45%, specificity 81%

Insulin dose-adjusted HbA1c (HbA1c plus four times units per kg per day) with a cut-off of 9 or below is widely used to define partial remission in paediatric type 1 diabetes, and as a trial eligibility or outcome measure. This study checked it against stimulated C-peptide in 422 youth from the SEARCH for Diabetes in Youth study, tested within 12 months of diagnosis.

Overall, IDAA1c of 9 or below had 61% sensitivity and 79% specificity for C-peptide of 0.91 ng/mL or more, with an area under the curve of 0.77. Among youth with overweight or obesity, sensitivity fell to 45% with specificity of 81%, because higher insulin requirements push the score up even when beta-cell function is better preserved. A cut-off of 11.6 raised sensitivity to 93% in this group but lowered specificity to 54%.

In clinic, a score above 9 in a child with excess weight does not mean the honeymoon has ended. Where beta-cell function matters for a decision or trial entry, C-peptide gives the better answer.

• IDAA1c of 9 or below caught only 61% of C-peptide-defined remission overall.
• In youth with overweight or obesity, sensitivity fell to 45%.
• A raised score does not exclude preserved insulin secretion in a child with excess weight.
• Consider stimulated or random C-peptide where remission status changes management or trial eligibility.
• A BMI-specific cut-off of 11.6 improved sensitivity but cost specificity, so it is not a ready fix.

Why it matters

A score built into trial criteria and clinic shorthand under-reads beta-cell function in exactly the children where obesity is rising.

Don't overread it

The cohort was US youth and a single cross-sectional comparison, so the proposed alternative cut-offs need validation before clinical use.

The statistics, in plain English

Sensitivity is the share of true remission cases the score detects; specificity is the share of non-remission cases it correctly excludes. A sensitivity of 45% means more than half of children in remission would be labelled as not in remission. Lowering the threshold catches more cases but wrongly includes more children who are not in remission.

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